A new book by a former high ranking U.S. official says the U.S. held confidential talks with Iran about Iraq's future ahead of the 2003 U.S.-led invasion that toppled Saddam Hussein.

According to his upcoming book, "The Envoy," former U.S. ambassador to Iraq, Zalmay Khalilzad says the previously undisclosed talks were held in Geneva and resulted in Iran promising not to fire at American warplanes that strayed into Iranian airspace. Excerpts from the book were published in the New York Times.

The book says Iran's ambassador to the U.N. and future foreign minister Mohammad Javad Zarif attended the meetings with the U.S. The book says talks continued even after U.S. troops seized the Iraqi capital Baghdad in April of 2003 but eventually stalled over differences on how to form a new Iraqi government and Tehran's support for terrorism. The administration of President George W. Bush is said to have halted the talks in May of that year.

In his book, Khalilzad writes “I am convinced that if we had combined diplomatic engagement with forcible actions, we could have shaped Iran’s conduct.”